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Ensuring Circuit Board Assembly Quality With AOI
Ensuring Circuit Board Assembly Quality With AOI
April 30, 2018

A circuit board assembly is as tailor-made as the customer so requires. The size of the board, intended function, density, reliability requirements and more will determine how the circuit board assembly will be designed. However, making sure that the final circuit board assembly meets the customer’s requirements comes down to quality testing.


Since circuit boards assemblies are manufactured at a very high rate and every board must be functional, an automated process is required; one which will correlate the expected board and the circuit board assembly actually produced.


This is the Automated Optical Inspection (AOI), a fast and accurate way of checking that the circuit board assembly coming off the production is fault-free. So how does AOI work?


  • Optical fault-finding – The circuit board assembly is well lit for the high definition and high speed cameras to assess numerous physical aspects of the board. The AOI builds a picture of the board for comparison. It detects surface features – scratches, stains, thin solder, incorrect or missing components


  • Image matching – The AOI is fed with the image of an accurately manufactured board, also known as a ‘golden board’. It is using this template that the AOI compares subsequently manufactured circuit board assembly. Other techniques include ‘algorithm’ learning: by this, the AOI builds a database of ‘good’ and ‘bad’ boards; or a statistical comparison model. In either case, the AOI allows minor acceptable deviation in the final circuit board assembly.


  • The image – AOIs may utilize one or more camera to capture the circuit board assembly. Multiple cameras allow the system to check accuracy on different planes. How the image is captured – whether by video or as a still image – depends on the pace of the production line. High sped production may choose to use the video system for acquiring an image, however this may not be as accurate as the still image system.


The placement of the AOI in the production process also serves an important function: place before time and cost-consuming processes, AOIs can help find faults before the circuit board assembly is completed.


Regardless, different production lines require a suitably tailored AOI system. The location and types of light source, the wavelength of the light, the image capture system and software are dependent on the kind of circuit board assembly and the pace of the production line. AOIs must be backed by a sufficiently robust computer hardware and software setup, given the large amounts of data that must be processed in a very short span.


Permatech Electronics has been a leading provider of printed circuit board assembly in the GTA for decades. Our ethos is underlined by constant improvement and education. We are compliant with latest best practices for electronics quality assurance and follow rigorous internal quality assurance standards.


We have a reputation for high quality yet cost-effective printed circuit board assemblies. Our boards are known to be more durable and effective than many of the other leading manufacturers in the field.

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